I dont think he builds all those cars. Perhaps in his younger years he may have done 2 or 3 but the rest would be done by workers following his ideas - or he wouldnt even have time to neither sleep nor pee!!!
Sbarro did also (way back in 1986) produce a Ferrari P4 replica, based on a Ferrari 308GTS chassis. Bodywork was more of a 'pastiche' than an attempt at accurate representation. Intitially, this car was built as a one-off customer commission. Much hype, including a full colour brochure followed, stating that 'production' cars would be based on the (subsequent) Ferrari 328GTS model. To the best of my knowledge, this car, which is still with the original owner, remains unique.